1. Field of the Invention
The present invention relates to a communication system and an e-mail check method.
2. Description of the Related Art
An e-mail system which exchanges information such as a message through a network is used widely. An e-mail is received by a predetermined mail reception protocol. A POP 3 (Post Office Protocol 3) is one of mail reception protocols which are widely used at present. However, a command for determining whether or not a new incoming mail is present is not provided in a POP3. Accordingly, when checking whether or not a new incoming mail is present, a user has to access to a mail server and to check her or his own mailbox.
Japanese Patent Application Laid-Open No. 2007-034559 discloses one solution for solving the above-mentioned problem. The official bulletin discloses a mobile terminal which automatically notifies a user of existence of a new incoming mail. Specifically, the mobile terminal periodically transmits a message for requesting a mail server to check a mail storage state and detects a change in a state from a previous mail storage state to check existence of a new incoming mail. Due to such a configuration, a user can recognize existence of a new incoming mail in real time without a user's unnecessary operation.
There are many kinds of forms for realizing an e-mail system. For example, there is an e-mail system in which one user has a plurality of communication devices (for example, a cellular phone and a personal computer) and accesses a common mail server from each of the communication devices to receive an e-mail. In such e-mail system, because a mail server receives access from a plurality of communication devices, a storage state of a received mail in a mailbox changes in a complicated manner in comparison with an e-mail system in which only one communication device accesses a mail server. Accordingly, a judgment of whether or not a new incoming mail is present becomes complicated.
However, the e-mail system disclosed in the above-mentioned official bulletin is not an e-mail system in which a plurality of communication devices access one mail server. Actually, a judgment of whether or not a new incoming mail is present described in the official bulletin is just a comparison between the last known storage state in a mailbox and a new known storage state. Accordingly, the above-mentioned problem of an e-mail system in which a mail server receives access from a plurality of communication devices and a storage state of a received mail in a mailbox intricately changes is not solved by the configuration disclosed in the official bulletin.